Google's cars are programmed to break the law in a number of scenarios. They will inch into an intersection if they don't sense that another car is going to take advantage of their right of way. They will speed faster than the posted limit if they sense that cars are traveling faster than that limit.

Obeying the law, in some scenarios, particularly when you might force people to make lane changes (which are dangerous in and of themselves) results in greater fatalities. In that situation, it makes sense to break the law.